1. Field
Embodiments disclosed herein generally relate to a magnetic read head for use in a hard disk drive.
2. Description of the Related Art
The heart of a computer is a magnetic disk drive which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected tracks on the rotating disk. The suspension arm biases the slider towards the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent a media facing surface (MFS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
One type of conventional magnetoresistive (MR) sensor used as the read head is a “spin-valve” sensor based on the giant magnetoresistance (GMR) effect. A GMR-spin-valve sensor has a stack of layers that includes two ferromagnetic layers separated by a nonmagnetic electrically conductive spacer layer. One ferromagnetic layer, typically called the “reference” layer, has its magnetization direction fixed, such as by being pinned by exchange coupling with an adjacent antiferromagnetic “pinning” layer, and the other ferromagnetic layer, typically called the “free” layer, has its magnetization direction free to rotate in the presence of an external magnetic field. With a sense current applied to the sensor, the rotation of the free layer magnetization relative to the fixed layer magnetization is detectable as a change in electrical resistance. If the sense current is directed perpendicularly through the planes of the layers in the sensor stack, the sensor is referred to as current-perpendicular-to-the-plane (CPP) sensor. Metallic CPP GMR sensor having low magnetoresistance is beneficial to increase signal to noise ratio, but the signal output of metallic CPP GMR sensor using transition magnetic metals is too low. In order to increase the signal output, Heusler alloy with high spin polarization is used in the reference layer.
However, Heusler alloy is deposited using high temperature and/or thick crystalline template, which may cause sensor performance to degrade. Therefore, an improved read head is needed.